Intravenous channel cardiac electrode and lead assembly and method

ABSTRACT

An intravenous lead assembly for atrial ventricular (AV) sequential pacing includes a channel and a separable core lead. The channel lead and the core lead respectively include first and second helical coil conductors through which first and second wire stylets can be inserted. The first and second helical coil conductors are embedded in first and second elongated silicone rubber sleeves, respectively. The silicone rubber sleeve of the channel lead includes an elongated channel. In use, the core lead is passed through the channel of the channel lead either before or after the channel lead is passed through selected veins into a patient&#39;s heart. Handles are provided on the proximal ends of the stylets to enable a physician to manipulate the distal ends of the channel lead and core lead. In one embodiment of the invention, the channel terminates in a side port of the channel lead, enabling the physician to guide the tip of the core lead out of the side port and into the right ventricle after the distal end of the channel lead has been positioned in the coronary sinus or the right atrial appendage.

This is a division of application Ser. No. 076,910, filed Sept. 19,1979, now U.S. Patent No. 4,332,259.

BACKGROUND OF THE INVENTION

1. Field of the Invention:

The invention relates to electrodes and leads for conducting electricalsignals to and from muscle tissue, and especially to electrodes andleads useful for intravenously conducting such signals to and fromendocardial electrodes.

2. Description of the Prior Art:

In the past, various types of endocardial leads and electrodes thereofhave been intravenously introduced into different chambers of apatient's heart, including the right ventricle, the atrium, the rightatrial appendage, and the coronary sinus. A typical endocardial leadincludes a sleeve composed of silicone rubber, which is resistent todeterioration caused by body fluids and does not cause adverse reactionby the patient's body. A helical coil embedded in the silicone rubbersleeve is electrically connected to a distal electrode which isintroduced into the heart and a proximal electrode electricallyconnected to the opposite end of the helical coil conductor to allowelectrical connection of the lead to electronic equipment, such as anelectronic pacemaker. Typically, a stylet made of thin spring steel wireand having a handle at one end thereof is removeably inserted throughthe length of the helical coil conductor. Turning of the handle permitsa physician to manipulate and control the distal end of the lead as itis intravenously introduced into the heart.

Both unipolar leads (including a single helical coil conductor embeddedin a single, silicone rubber sleeve) and bipolar leads (including twohelical conductors embedded in a single silicone rubber sleeve) havebeen utilized. Such intravenous leads are readily available from variousmanufacturers, including Cardiac Pacemakers, Inc., of St. Paul, Minn.,Inter-Medics, Inc., of Freeport, Texas, and Med-Tronic, Inc., ofMinneapolis, Minn.

Recently, surgeons have attempted to introduce several leads into theheart of a patient in order to accomplish atrioventricular (AV)sequential pacing, which has been made possible by recently developed AVsequential pulse generators. AV sequential pacing makes it possible forthe heart of a patient to achieve maximum cardiac output by causing theupper and lower chambers of the heart to fire in optimum time sequencesuch that the receiving chamber can receive an optimum amount of blood,which can then be pumped in proper time sequence to the periphery of thebody.

Ordinarily, the cephalic veins at the shoulder level or the internal orexternal jugular veins in the neck of a patient are surgically openedand endocardial leads are introduced through the respective venousopenings. The desirability of inserting two endocardial leads to achieveAV sequential pacing has posed a problem to the surgeon, since two(rather than only one) incisions must be made in two veins which havecontinuity with the right side of the heart in order to pass twoendocardial leads intravenously into the heart. The leads must be passedparallel to each other through the accessible veins. This situation canresult in dislodgement of a first lead which has been initially insertedinto a proper position in the heart. Further, when multiple leads arelodged in different portions of the heart, the leads sometimes rubagainst each other due to lead flexing caused by beating of the heart.The forces produced as a result of the rubbing sometimes causedislodging of electrodes attached to the leads. There is presently aunmet need for a reliable system for introducing multiple endocardialleads intravenously into the heart without the surgical complexity thatnow exists.

Accordingly, it is an object of the invention to provide a system andmethod of intravenously introducing an endocardial lead into a patient'sheart with minimum danger of dislodging an endocardial lead previouslyintroduced and lodged within the patient's heart.

It is another object of the invention to provide a system and method ofintravenously introducing an endocardial lead into a patient's heartwithout the requirement that individual leads be passed through separateincisions into one or more veins of the patient.

It is another object of the invention to provide an endocardial leadsystem which avoids rubbing between leads due to flexing of the leadscaused by beating of the heart in which the leads are lodged.

It has been very difficult to introduce prior endocardial leads into thecoronary sinus or to attain the J-shaped curvature necessary to attachan electrode to the right atrial appendage, as is desirable in someinstances to attain AV sequential pacing. U.S. Pat. Nos. 3,865,118;4,057,067; and 4,154,247 disclose endocardial leads designed to makeatrial contact. The device disclosed in patent 3,865,118 includes acatheter of coaxial design. This device includes spring electrodesconnected to both inner and outer conductors for contacting the apex ofthe ventricle and outer atrium, respectively. This device does not allowthe controlling of the positions of the leads, except as to their depth,by the physician. Further, spring electrodes can be a source of clotformation. Further, due to the springing characteristic of electrodes,laceration or perforation of the vena cava can occur. Further, thedisclosed device is incapable of contacting optimum muscle tissuelocations in the heart to accomplish optimum AV sequential pacing.Further, repositioning of the distal spring electrodes after initiallodging in heart muscle tissue may be dangerous.

It is another object of the invention to provide a multiple leadendocardial lead assembly and method which enables a surgeon toindependently control the depth of insertion of a second lead into asecond heart chamber, after a first lead has been inserted into a firstheart chamber.

It is another object of the invention to provide a multiple leadendocardial lead assembly which does not depend upon springiness of alead to maintain electrode contact with muscle tissue of the heart.

It is another object of the invention to provide a multiple leadendocardial lead assembly which has no tendency to lacerate heart tissueas a result of continual beating of the heart for a very long period oftime.

The device disclosed in Patent 4,057,067 discloses a single bipolar leadstructure having an atrial electrode structure which assumes a J-shapedconfiguration, enabling the atrial electrode to be hooked onto theatrial appendage at the time the ventricular component and the electrodethereon is firmly engaged against the right ventricular wall. Duringinsertion, a stylet maintains the atrial component in a linearconfiguration. When the stylet is removed the atrial component springsinto the desired J-shaped configuration. This device has the problemthat the lengths of the ventricle and atrial tipscannot be adjusted forvarious sized hearts or anatomical configuration. Further, the ventricletip can become dislodged when the atrial component is released bywithdrawing the stylet. The device is not suitable for stimulatingtissue in the coronary sinus.

It is another object of the invention to provide a multiple leadendocardial lead assembly which allows independent adjustment of thedepth of one of the leads after another of the leads has been positionedin the heart, and is suitable for insertion of one lead into either thecoronary sinus or the atrial appendage and is also suitable forinsertion of another lead into the right ventricle.

The device disclosed in Patent 4,154,247 discloses a bipolar leadincluding a sheath having an insulating layer which, when heated, byimmersing it into boiling water, enables the lead to be formed into aparticular configuration. When the lead cools, it "sets" into a newdeformable configuration. The device has the shortcoming that it is abipolar lead having two electrodes disposed along a single lead. Itrelys on its deformed configuration to maintain spring pressure of theelectrode against suitable portions of the ventricle and atrium. Thisresults in unreliable electrical contact to tissue in a beating heart.The device is not suitable for contacting muscle tissue both of theventricle and the coronary sinus, and provides minimal capacity formanipulation of the electrodes by a physician.

Accordingly, another object of the invention is to provide a multiplelead endocardial assembly and method which overcomes the aboveshortcomings of prior endocardial leads.

SUMMARY OF THE INVENTION

Briefly described, and in accordance with one embodiment thereof, theinvention provides an intravenous composite lead assembly for conductingsignals between an electronic floating device such as anatrioventricular pacemaker and various muscles in a patient's heart. Thecomposite lead assembly includes a channel lead and a core lead, each ofwhich has a proximal end for connection to the pacemaker unit and adistal end for connection to electrodes which electrically contactendocardial tissue. The channel lead includes an elongated channel whichextends along a substantial portion of the channel lead to a portlocated at a predetermined distance from the distal end of the channellead. The port may be either an end port or a side port. The core leadcan be slid through the channel of the channel lead and caused to extendfrom the side port. The channel lead and core lead are each formed ofsilicone rubber, and each includes at least one flexible conductorsurrounded by silicone rubber and extending from the proximal end of thelead to an electrode located at or near the distal end of that lead.

In use, the channel lead can be introduced into a venous path leading tothe heart through only one incision, usually made in the cephallic vein,the subsclavian vein, or the internal jugular vein. In one embodiment ofthe invention, the channel lead normally assumes a J-shapedconfiguration or an L-shaped configuration to allow convenientpositioning of the distal electrode of the channel lead with tissue ofthe right atrial appendage or the coronary sinus. A wire stylet whichmaintains the distal end of the channel lead in a relatively straightconfiguration is withdrawn when the distal end of the channel lead isadvanced to a particular location in the heart. This causes the distalend of the channel electrode to spring into its normal J-shaped orL-shaped configuration. Next, the core lead is passed through thechannel lead, and exits from the channel through the side port and intothe right ventricle. Usually, the vein will be tied around the channellead to maintain it in proper position before the core lead is passedthrough the channel. Once the core lead is in its proper place in theright ventricle, ties are utilized to tighten the proximal end of thechannel against the outer surface of core lead to prevent leakage ofblood out of the heart through the channel. Sealing ridges are providedon the proximal ends of the channel lead and core lead. The distal endsof the conductors of the core lead and channel lead are plugged intorecepticles of a pacemaker unit. The pacemaker unit has flexible sleeverecepticles which slide over sealing ridges of the respective proximalends of the channel electrode and core electrode. Ties are utilized totighten the flexible recepticles against the sealing rings to preventleakage of blood into the pacemaker unit.

The core lead and channel lead can be either unipolar or bipolar, thebipolar leads each having two flexible conductors and two distalelectrodes, and the unipolar leads having only one flexible conductorand one distal electrode.

If desired, the core lead may be positioned in the channel of thechannel lead and the composite assembly may be entered as a unit throughthe single venous incision. If desired, a core lead can be preformed, sothat it can spring into an L-shaped or J-shaped configuration when astylet or stylets of the core lead are withdrawn; the distal end of thechannel lead in this case must be initially fed into the rightventricle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a partial perspective view of a unipolar composite leadassembly.

FIG. 1B is a partial perspective view of a unipolar core lead in thecomposite lead assembly of FIG. 1A.

FIG. 1C is a partial perspective view of the proximal end of a unipolarchannel lead of the composite lead assembly of FIG. 1A.

FIG. 2 discloses a sectional view along section lines 2--2 of FIG. 1A.

FIGS. 3 and 4 disclose alternate sectional configurations which can beused for a unipolar composite lead assembly similar to that of FIG. 1A.

FIG. 5 is a partial exploded perspective view of a composite bipolarchannel lead assembly.

FIG. 6 is a partial cutaway side view of the proximal end of the bipolarcore lead assembly of FIG. 5 with the core lead inserted in the channellead.

FIG. 7 is a section view along section lines 7--7 of FIG. 5.

FIG. 8 is a partial side view of a bipolar electrode tip which can beused on the bipolar core or channel leads of the composite lead assemblyof FIG. 5.

FIG. 9 is a side view of another bipolar electrode tip which can be usedwith a bipolar core lead or channel lead.

FIG. 10 is a side view of another bipolar electrode tip which can beused with a bipolar core lead or channel lead.

FIG. 11 is a side view of the proximal end of a composite lead assemblyincluding a channel lead with an end port through which a core leadextends.

FIG. 12 shows a partial view of a human heart with the compositeendocardial lead assembly of FIG. 5 positioned in the heart so that thechannel lead proximal electrodes contact tissue of the right atrialappendage and the core lead distal electrodes contact tissue of theright ventricle.

FIG. 13 is a partial view of a human heart showing the compositeunipolar channel lead assembly of FIG. 1A, with its core lead distalelectrode contacting tissue of the right ventricle and its channel leaddistal electrode contacting tissue in the coronary sinus.

FIG. 14 discloses a composite electrode wherein the channel lead has anend port with an end port electrode connected to contact the atrialtissue and a core lead extending into the right ventricle.

FIG. 15 is a flow chart illustrating the method of one embodiment of theinvention.

DESCRIPTION OF THE INVENTION

Referring now to FIGS. 1A-1C and FIG. 2, and particularly to FIG. 1B,core lead 1 is a typical endocardial lead including an elongatedflexible silicone rubber sheath 13 through which a helical coilconductor 25 extends. Any of a variety of tips, such as ones similar tothose shown in FIGS. 8-10, can be provided at the right end of tip 1"referred to as the distal end of core lead 1. Tip 1" includes electrode31 for conducting electrical signals to or from muscle tissueelectrically contacted by electrode 31 (which is referred to as a distalelectrode).

At the left-hand end of core lead 1, referred to as the proximal end 1,a proximal prong or electrode 5 electrically contacts helical coilconductor 25 and extends beyond silicone rubber sleeve 13. A fine springwire stylet 7 having a predetermined bend therein extends throughhelical coil conductor 25 to the distal end of core lead 1. Stylet 7 hasa small handle 11' attached thereto. Handle 11' can be used for rotatingstylet 7 to control the distal end 1" of core lead 1 and can also beused to withdraw stylet 7 from core lead 1, whereupon proximal electrodeor prong 5 can be inserted into an electrical connector of a suitableelectronic device, such as a cardiac pacemaker.

Referring now particularly to FIG. 1C, channel lead 3 includes abifurcated Y-shaped proximal end structure 3' including a helical coilconductor 9 extending through one leg of the structure and through themain portion 26 of the channel lead. A second prong or electrode 23extends from the first leg of the structure, and electrically contactsthe proximal end of helical coil conductor 9. At the distal end ofchannel lead 3' (FIG. 1A) a suitable electrode, such as 35, is attachedto the distal end of helical coil conductor 9. A hollow channel 17extends through the second leg of channel lead 3' and continues parallelto helical coil conductor 9 through the main portion 26 of channel lead3'. A wire stylet 21 having a handle 19 connected thereto extendsthrough helical coil conductor 9 in the same manner that stylet 7extends through core conductor 1.

FIG. 1A shows the proximal end 27' of a composite channel lead 27including channel lead 3' FIG. 1C and core lead 1 of FIG. 1B insertedthrough channel 17 of channel lead 3'. A pair of the leg ties 36 causesthe end of leg through which channel 12 extends 17 to be crimped tofrictionally engage the outer surface of core lead 1, maintaining it infixed relationship to channel lead 3', preventing body fluid from beingpumped out of the heart through the space between the outer wall of corelead 1 and the inner wall of channel 17 of channel lead 3'.

FIG. 1A also shows the distal end 27" of composite unipolar channel lead27, wherein it is seen that channel 17 of channel lead 3' terminates ina side port 29 of distal end section 27". Side port 29 includes aconcave curved surface which directs core lead 1 outward from side port29. As subsequently explained, this enables a surgeon to insert thecomposite unipolar channel lead 27 through a vein and facilitatespositioning of the distal end of the channel lead tip 35 into either theright atrial appendage or the coronary sinus and then allows subsequentsliding of core lead 1 through channel 17 and out of side port 29,facilitating introduction of the tip 33 of core lead 1 into the rightventricle.

FIG. 3 shows a sectional view of a slightly modified embodiment of thecomposite lead assembly wherein body section 26 of the channel lead 3'has an eliptical configuration.

FIG. 4 discloses a sectional view of another embodiment wherein section26 of the channel lead has a channel 17 with a semi-circularconfiguration and wherein the core lead 1 has a correspondingsemi-circular cross-sectional configuration. The semi-circularconfiguration of the channel and core lead prevent any rotation of thecore lead in the channel as the core lead is slid through the channellead, which may have been previously intravenously introduced into thepatient's heart.

Referring now to FIGS. 5-7, and particularly to FIG. 5, a bipolarchannel lead assembly 41 which includes bipolar channel lead 37 andbipolar core lead 39 is shown. The proximal end 37' of bipolar channellead 37 includes a silicone rubber sleeve 49 having a bifurcated endwith legs 37A and 37B which join to form a unitary shaft 37C.

A channel 57, similar in purpose to channel 17 of FIG. 1B, has anenlarged entrance opening 55 disposed between legs 37A and 37B. A firsthelical coil conductor 53A extends through leg 37A and through unitarysection 37C on one side of channel 57. A second helical coil conductor53B extends through leg 37B and through unitary section 37C on theopposite side of channel 57.

Prongs or proximal electrodes 47A and 47B extend from the siliconerubber material of legs 37A and 37B and are electrically connected tohelical coils 53A and 53B, respectively. Spring wire stylus 45A extendsthrough prong 47A and helical conductor 53A. Stylet 45B extends insimilar fashion through prong 47B and helical conductor 53B. Handles 43Aand 43B are respectively connected to the proximal ends of stylets 45Aand 45B.

Still referring to FIG. 5, bipolar core lead 39, which mates withbipolar channel lead 37, also includes a pair of bifurcated leg sections39A and 39B and a unitary section 73. Helical conductor 69A extendsthrough leg 39A and unitary section 73. Wire stylet 61A extends throughhelical conductor 69A. Similarly, helical coil conductor 69B extendsthrough leg 39B and unitary section 73. The body of bipolar core lead 39supports and surrounds helical conductor 69A and 69B and is formed ofsilicone rubber. Prongs or proximal electrodes 63A and 6B are connectedto the proximal ends of helical coil conductors 39A and 39B, and extendfrom the proximal ends of legs 39A and 39B, respectively. Handles 59Aand 59B permit manipulation of stylii 61 A and 61B, respectively.

Legs 39A and 39B of bipolar core lead 39 come together at a taperedsection 67, which terminates at a cylindrical ridge 71. Cylindricalridge 71 fits into enlarged channel opening 55 of FIG. 6, therebylimiting the extent to which unitary section 73 can be inserted intochannel 57 of bipolar channel lead 37.

Referring now to FIG. 6, a side view of the composite bipolar channellead assembly 41 is shown. The side view bipolar channel lead assembly41 in FIG. 6 includes bipolar channel lead 37 with bipolar core lead 39inserted in place, with section 73 of bipolar core lead 39 extendingthrough channel 57 of bipolar channel lead 37.

Ties 65 compress channel opening 55 against the ridge 71 of unitarysection 73, causing bipolar core lead 39 to remain in fixed relationshipwith bipolar channel lead 37 and prevent body fluids from being pumpedthrough the space between the wall of channel 57 and unitary section 73of core lead 39.

The distal end of composite bipolar channel lead assembly 41 is shown inFIG. 5, a sectional view of which is shown in FIG. 7. In FIG. 5 it isseen that channel 57 terminates in side port 77 (in the same manner thatchannel 17 of FIG. 1A terminates in side port 29). Concave surface 79causes section 73 of bipolar core lead 39 to be directed outwardly fromthe axis of bipolar channel lead section 73C as unitary section 73 isforced through channel 57 and out of side port 77. This facilitatescontrolling the orientation of bipolar core lead 39 by a surgeon as heattempts to insert the distal end of bipolar core lead 39 into the rightventricle of the patient's heart after the core lead has first beenpositioned in the coronary sinus or the right atrial appendage.

FIGS. A-11 illustrate several lead tips which can be used with the abovedescribed bipolar channel lead and core lead. FIG. 8 shows a bipolarlead tip which includes spaced electrodes 113 and 114, electrode 114being spaced from the extreme end of the bipolar tip. This bipolar leadtip can be attached to the end of any bipolar channel lead or core lead.FIG. 9 discloses a conventional bipolar lead tip with a wedge shapedelectrode at its extreme end and a cylindrical electrode spaced from thewedge shaped electrode. FIG. 11 discloses another bipolar lead tipincluding a pair of folding tine electrodes at its extreme end and acylindrical electrode spaced from the tine electrode. A laterallyslideable cap 123 causes the tines to fold in, as indicated by 105A, orextend out, as indicated by 105. The laterally slidable cap 123 slideslaterally when the enlarged electrode at the extreme right hand end ofsection 1" in FIG. 14 is forced out of end port 20'.

FIGS. 12 and 13, and 14 show several ways in which the composite leads27 (FIG. 1) and 37 (FIG. 5) can be positioned in a patient's heart.

FIG. 12 shows the bipolar composite channel lead assembly 37 of FIG. 5extending through the cephallic vein 89, the subclavian vein 87, and theinnominate vein 91. The distal end 37" of channel lead assembly 37springs into a J-shaped configuration as shown in FIG. 12 when stylii45A and 45B (FIG. 5) are withdrawn. The electrodes on the end of channellead 37 then make electrical contact with the right atrial appendage.

Section 73 of core lead 39 extends from side port 77 so that its twoelectrodes 85 and 85' electrically contact appropriate tissue in theright ventricle 83. (For convenience of illustration, the handles ofstylii 45A and 45B are not shown as being withdrawn in FIG. 12, eventhough distal end 73" has sprung into the J-shaped configuration. Arrows108 of FIG. 12 indicate that stylii 45A and 45B (FIG. 5) are withdrawnto allow distal end 73" to spring into the J-shaped configuration).

It should be noted that a surgeon can completely insert compositechannel lead assembly 37 into the heart with the core lead 39 insertedinto chanel 57 but not extending out of side port 77, withdraw stylii45A and 45B so that distal end 37" bends to contact the right atrialappendage, and then slide core lead 39 further through channel 57 sothat section 73 of core lead 39 extends out of side port 77 and travelsa predetermined distance into the right ventricle 83.

Alternately, the surgeon can first insert channel lead 37 alone throughthe cephallic, subclavian, and innominate veins, withdraw stylii 45A and45B, causing the distal end 37" to bend to contact the right atrialappendage. Then, the surgeon can insert core lead 39 into channel 57 andslide it through channel 57 until distal end 73 of core lead 37 passesout of side port 77 and reaches the appropriate part of the rightventricle.

Next, the physician tightens "ties" 65 (FIG. 6) around flexiblerecepticle 55, sealing channel 57 with respect to core lead 37 toprevent blood from seeping through channel 57.

Next, the surgeon removes stylii 61A and 61B (FIG. 5) and inserts prongs63A, 63B, 47A, and 47B into the appropriate female recepticles of apacemaker unit or the like. The pacemaker unit has silicone rubberrecepticle sleeves which slide over sealing ridges 51 and terminalsealing ridges 51' of the proximal ends of the respective leads. Tiessimilar to ties 65 (FIG. 6) are utilizled to seal the proximal ends ofchannel lead 37 and core lead 39 with respect to the pacemaker unit (notshown) to prevent blood from seeping into the pacemaker electroderecepticles.

In FIG. 13, unipolar channel lead assembly 27 has been introduced intothe heart through cephallic vein 89, subclavian vein 87, and innominatevein 91. Distal end 3" and its corresponding electrode extend intocoronary sinus 111. Distal end 1" of core lead 1 extends out of sideport 29 of channel lead 3 into ventricle 83.

The presently preferred technique is to utilize a channel lead 3' whichis performed so that when wire stylet 21 is withdrawn, distal end 3"springs into an L-shaped configuration which causes distal end 3" tomove into coronary sinus 111. When distal end 3" reaches the end ofcoronary sinus 111, core lead 1 is inserted into channel 17 of channellead 3' and passed through channel 17 until distal end 1" passes out ofside port 29 and extends into the desired location of right ventricle83. Alternately, however, composite channel electrode 27 can beintroduced as a unit through the venous path shown in FIG. 13. Asbefore, ties such as 36 (FIG. 1A) must be applied to prevent leakage ofblood after the electrodes of distal end 3" of core lead 3 and 1" ofcore lead 1 are properly lodged in the coronary sinus and rightventricle, respectively.

FIG. 14 discloses unipolar channel lead assembly 27 inserted throughinternal jugular vein 101, innominate vein 91 through the atrium andinto right ventricle 83. The embodiment of bipolar channel lead assembly27 shown in FIG. 14 has an end port 29. (FIG. 11 shows in detail thestructure of the distal electrodes of FIG. 14, wherein electrode tines105 are attached to the extreme end of channel lead 5. When the abovementioned laterally slidable cap shown in FIG. 11 slides forward, thefoldable tines indicated by reference numeral 105A spring outward asindicated by reference numeral 105. The channel of channel lead 5terminates in an end port 29' located at the extreme distal end 3" ofchannel lead 3. The distal end 1" of core lead 1 extends out of end port29'). Electrode 103 of distal end 3" of channel lead 3 has a pair oftines 105 which are actuated by forward movement of the above-mentionedlaterally slidable cap 123, as shown in FIG. 11, but not shown in FIG.14 to hook into the atrial tissue. Distal end 1" of core lead 1 haselectrode 11', which engages muscle tissue in the right ventricle 83.Ties 36 seal the channel of channel lead 3 with respect to core lead 1.Again, composite channel lead assembly 27 can be fed into heart 81 as asingle unit, or channel lead 3 first can be introduced into the heartalone, and then core lead 1 can be slid through channel 17 of chanellead 3, so that the distal end 1" of core lead 1 passes through end port29' until it reaches its final destination in ventricle 83.

It should be noted, however, that although the lead placements shown inFIGS. 12 and 13 are presently preferred, it is also possible to reversethe roles of the distal ends of the channel and core leads, so that thecore "springs" into the J-shaped configuration necessary to contact theright atrial appendage or pass into the coronary sinus when the corelead stylet or stylii are withdrawn, after which time the distal end ofthe channel lead is passed into the right ventricle. The latterapproach, however, may cause some difficulty, since more skillfulmanipulation is required to place leads in the right atrial appendage orthe coronary sinus. It is believed to be best to position and lodge alead in the atrial appendage or coronary sinus first since it is usuallya relatively simple matter to position and lodge a lead in the rightventricle.

As previously mentioned, intravenous insertion of a channel lead into apatient's heart can be accomplished with the core lead positioned in thechannel at the time of introduction of the channel lead and through anappropriate venous entry site. Alternatively, if passage of the corelead tip is compatable with the diameter of the channel such that thecore lead tip can be passed through the channel after the channel leadhas been positioned in the patient's heart, then the channel lead may beintroduced into an appropriate venous incision, through an intravenouspathway to the heart, and into the appropriate heart chamber without thecore lead being positioned in the channel of the channel lead. If thelatter method is employed, the open channel of the channel lead firstcan be filled with a sterile intravenous solution, such as normal salinesolution. The proximal channel opening can then be connected to a pumpthat produces a controlled rate of intravenous infusion of normal salinesolution, so that no blood will flow into the channel (possiblyproducing clots or blood loss) during passage of the open-channelchannel lead into the venous entry site. The flow chart of FIG. 15illustrates the foregoing procedure. Alternatively, after the channel isfilled with a sterile solution (such as the above mentioned normalsaline solution), the proximal end of the channel can be capped duringintroduction of the open-channel channel lead into the selected venousentry site.

While the invention has been described with reference to severalembodiments thereof, those skilled in the art will be able to makevariations in the disclosed structure and method which are well withinthe purview of those skilled in the art without departing from the truespirit and scope of the present invention. For example, a plurality ofsilicone rubber straps or clips integrally formed with one lead couldslideably engage a second lead against the first lead. This approachwould work in situations wherein it is acceptible to introduce acomposite lead through a venous path into the heart. However, thisapproach would not work if it were desirable to first introduce one leadinto the heart, since it would be impossible to pass the free end of asecond lead through the silicone rubber straps or clips.

I claim:
 1. A method for intravenously introducing first and secondleads into a patient's heart, said method comprising the steps of:(a)making only one incision in only one vein in a venous path leading tothe patient's heart; (b) inserting a first end of a channel lead intothe vein through the incision, the channel lead having a first end and asecond end, the channel lead having an elongated channel terminating ina side port opening located a predetermined distance from the second endof the channel lead, the channel being capable of accommodating passingof a core lead through the channel, the core lead having a first end anda second end; (c) guiding the first end of the channel lead through avenous path to the entrance of a first predetermined cavity of thepatient's heart; (d) withdrawing first and second stylets from thechannel lead, the channel lead being preformed to assume a bentconfiguration with a bend located approximately at the location of saidside port opening when the first and second stylets are withdrawn inorder to direct the first end of the core lead into said predeterminedcavity in the patient's heart adjacent to said venous path, said chanellead being preformed to tend to assume said bent configuration to causethe second end of said channel lead to move into said predeterminedcavity of the patient's heart when the stylet is removed, said side portopening being located near the lowest portion of said bend when thesecond end of said channel lead is in the deepest portion of saidpredetermined cavity; (e) guiding the first end of said channel leaddeep into said predetermined cavity; and (f) guiding the first end ofsaid core lead through the channel, out of said side port opening, intothe right ventricle of the patient's heart.
 2. A lead assembly forintravenously conducting electrical signals through a venous path to orfrom a patient's heart, the lead assembly comprising in combination:(a)a core lead having first and second ends, said core lead including(i)first flexible sleeve means; (ii) a first conductor surrounded bymaterial of said first flexible sleeve means, said first conductorextending approximately between the first and second ends of said corelead; (iii) first electrode means attached to said first flexible sleevemeans approximately at the first end of said core lead, said firstelectrode means being electrically connected to said first conductor;(iv) a second conductor surrounded by material of said first flexiblesleeve means, said second conductor being spaced from and electricallyinsulated from said first conductor, said second conductor extendingapproximately between the first and second ends of said core lead; (v)second electrode means attached to said first flexible sleeve means afirst predetermined distance from said first electrode means, saidsecond electrode means being electrically connected to said secondconductor; (b) a first removable stylet extending through said firstflexible sleeve means to facilitate control of said core lead, said corelead being preformed to tend to assume a straight configuration whensaid first stylet is removed from said core lead; (c) a channel leadhaving first and second ends, said channel lead including(i) secondflexible sleeve means, said second flexible sleeve means having anelongated channel for receiving said core lead, said channel extendingthrough a major portion of the length of said channel lead, said channelextending from a first opening in said channel lead to a second openingin said channel lead, said first opening being located at said first endof said channel lead, said second opening being a side port openinglocated a first predetermined distance from said second end of saidchannel lead; (ii) a third conductor surrounded by material of saidsecond flexible sleeve means, said third conductor being disposedoutside of said channel and extending approximately between the firstand second ends of said second flexible sleeve means; (iii) thirdelectrode means attached to said second flexible sleeve meansapproximately at the first end of said channel lead, said thirdelectrode means being electrically connected to said second conductor;(iv) a fourth conductor surrounded by material of said second flexiblesleeve means, said fourth conductor being disposed outside of saidchannel and extending approximately between the first and second ends ofsaid second flexible sleeve means; (v) fourth electrode means attachedto said second flexible sleeve means a second predetermined distancefrom said third electrode means; and (d) a second removable styletextending through said second flexible sleeve means to facilitatecontrol of said channel lead, said core lead being disposed in saidchannel lead, the first end of said core lead extending from said firstopening and the second end of said core lead extending from said secondopening, said first opening being located within the patient's heartwhen said channel lead is positioned to conduct the electrical signalsto a predetermined portion of the patient's heart, said channel leadbeing preformed to tend to assume a bent configuration with a sufficientamount of bending located approximately at the location of said sideport opening to cause said second end of said channel lead to move intoa predetermined cavity in the patient's heart adjacent to said venouspath when said second stylet is removed, said side port opening beinglocated near the entrance to said predetermined cavity when the secondend of said channel lead is in the deepest portion of said predeterminedcavity, said core lead extending slidably through said side port openingdeep into the right ventricle of the patient's heart.
 3. The leadassembly of claim 2 including a third removable stylet extending throughsaid first flexible sleeve means to facilitate control of said corelead.
 4. The lead assembly of claim 2 including a third removable styletextending through said second flexible sleeve means to facilitatecontrol of said channel lead.